Pressure balanced shaft seal assembly

ABSTRACT

A pressure balanced shaft seal assembly that allows a seal to dynamically respond to angular or radial misalignment of a shaft is disclosed. The pressure balanced shaft seal assembly includes a fixed stator, a floating stator, and a labyrinth seal. In one embodiment, the floating stator and labyrinth seal are mounted within an annular groove formed in the fixed stator such that the floating stator and labyrinth seal may move a predetermined amount in the radial direction with respect to the fixed stator. A spherical interface between the labyrinth seal and floating stator may allow the labyrinth seal to pivot with respect to the floating stator during angular misalignment of a shaft around which the pressure balanced shaft seal assembly is mounted. A pressure balancing annular channel formed in the floating stator allows pressurized seal fluid to balance the axial pressure exerted on the floating stator by the process fluid.

Applicant states that this utility patent application claims priorityfrom U.S. patent application Ser. No. 12/156,476 filed May 30, 2008, andis a continuation-in-part of said utility patent application, whichclaimed priority from U.S. patent application Ser. No. 11/405,207 filedApr. 17, 2006 (now U.S. Pat. No. 7,396,017) as a continuation of saidutility patent application, which claimed priority from both U.S. patentapplication Ser. No. 10/177,067 filed Jun. 21, 2002 (now U.S. Pat. No.7,090,403), as a continuation in-part, and Provisional Pat. App. No.60/697,434 filed Jul. 9, 2005, all of which are incorporated byreference herein.

FIELD OF THE INVENTION

The present invention relates to a pressure balanced shaft seal assemblywith multiple embodiments. A labyrinth seal for retaining lubricationsolution within the bearing cavity of a hub assembly, such as a bearinghousing, for application to a rotatable shaft to keep contaminants outof the bearing cavity while allowing a sealing fluid to balance thepressure on the process sides of the seal is disclosed and claimed. Inanother embodiment, the pressure balanced shaft seal assembly may beused as a product seal between a product vessel and a shaft therein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

No federal funds were used to create or develop the invention herein.

REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTINGCOMPACT DISK APPENDIX

Not Applicable

BACKGROUND OF THE INVENTION

For years there have been a multitude of attempts and ideas forproviding a satisfactory seal when a rotatable shaft is angularlymisaligned resulting in run out of the shaft. Typically the solutionspresented have failed to provide an adequate seal while allowing for anacceptable amount of shaft misalignment during operation. The problem isespecially acute in product seals where the potential for shaft to boremisalignment may be maximized. A typical solution in the prior art is toincrease the operating clearance between the rotating shaft and sealingmembers to create a “loose” clearance or operating condition. “Loose”running for adjustment or response to operational conditions, especiallymisalignment of the shaft with respect to the stator or stationarymember, however, typically reduces or lowers the efficiency and efficacyof sealing members.

Labyrinth seals, for example, have been in common use for many years forapplication to sealing rotatable shafts. A few of the advantages oflabyrinth seals over contact seals are increased wear resistance,extended operating life and reduced power consumption during use.Labyrinth seals, however, also depend on a close and defined clearancewith the rotatable shaft for proper function. Shaft misalignment is alsoa problem with “contact” seals because the contact between the seal andmisaligned shaft typically results in greater wear. Abrasiveness of theproduct also affects the wear pattern and the useful life of the contactseals.

Prior attempts to use fluid pressure (either vapor or liquid) to sealboth liquid and solid materials in combination with sealing members suchas labyrinth seals or contact seals have not been entirely satisfactorybecause of the “tight” or low clearance necessary to create the requiredpressure differential between the seal and the product on the other sideof the seal (i.e., the tighter the seal, the lower the volume of fluidrequired to maintain the seal against the external pressure ofmaterial.) Another weakness in the prior art is that many product sealsexpose the movable intermeshed sealing faces or surfaces of the productseal to the product resulting in aggressive wear and poor reliability.Furthermore, for certain applications, the product seal may need to beremoved entirely from the shaft seal assembly for cleaning, because ofproduct exposure to the sealing faces or surfaces.

In many shaft sealing systems, especially pump housings, the product ispressurized above ambient conditions and exerts a force on the interiorsurface of the seal, which may cause excessive wear on the seal.

The prior art then has failed to provide a solution that allows both a“tight” running clearance between the seal members and the stationarymember for efficacious sealing and a “loose” running clearance foradjustment or response to operational conditions especially misalignmentof the rotatable shaft with respect to the stator or stationary member.

SUMMARY OF THE INVENTION

The present art offers improved shaft sealing and product sealperformance over the prior art. The shaft seal assembly solutiondisclosed and claimed herein allows both tight or low running clearancebetween seal members and the stationary member and a loose runningclearance for adjustment or response to operational conditionsespecially misalignment of a rotatable shaft with respect to the statoror stationary member.

As disclosed herein, the present art describes and provides for improvedfunction by allowing a labyrinth seal to adjust to radial, axial andangular movements of the shaft while maintaining a desiredshaft-to-labyrinth clearance. The present art also permits equalizationof pressure across the labyrinth pattern by permitting venting and thusimproved function over currently available designs. Additionally,sealing fluid (air, steam, gas or liquid) pressure may be appliedthrough the vent or port locations to establish an internal sealpressure greater than inboard or outboard pressure(over-pressurization). This enables the labyrinth to seal pressuredifferentials that may exist between the inboard and outboard sides ofthe seal. Pressurization of the internal portion of the shaft sealassembly effectively isolates the moving or engaging faces of the shaftseal assembly from contact with product by design and in combinationwith a pressurized fluid barrier.

It is therefore an object of the present invention to provide a shaftseal assembly for engagement with a housing which maintains its sealingintegrity with a shaft upon application of axial, angular or radialforce upon said shaft.

It is another object of the present invention to provide a shaft sealassembly, which may be mounted to a vessel wall for engagement with ashaft which maintains its sealing integrity with a shaft during or inresponse to axial, angular or radial force movement of said shaft.

Yet another object of the present invention is to provide a pressurebalanced shaft seal assembly wherein a sealing fluid or lubricant may beincorporated into the seal assembly and at least partially counter actthe force exerted onto the process side of the seal assembly.

Other objects and features of the invention will become apparent fromthe following detailed description when read with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of the invention will be readilyunderstood, a more particular description of the invention brieflydescribed above will be rendered by reference to specific embodimentsillustrated in the appended drawings. Understanding that these drawingsdepict only typical embodiments of the invention and are not thereforeto be considered limited of its scope, the invention will be describedand explained with additional specificity and detail through the use ofthe accompanying drawings.

FIG. 1 is a perspective exterior view of the shaft seal assembly.

FIG. 2 is an exterior end view of the shaft seal assembly with the shaftelement aligned.

FIG. 3 is a sectional view of a first embodiment of the shaft sealassembly, as shown in FIG. 2 and mounted to a housing.

FIG. 3A illustrates the first surface seal-shaft integrity duringangular and radial shaft alignment.

FIG. 3B illustrates second surface seal-shaft integrity during angularand radial shaft alignment.

FIG. 4 is an exterior end view with the shaft misaligned.

FIG. 5 is a sectional view of the first embodiment as shown in FIG. 3with both angular and radial misalignment of the shaft applied.

FIG. 5A illustrates first seal-shaft integrity allowed by articulationduring angular and radial shaft misalignment.

FIG. 5B illustrates second seal-shaft integrity allowed by articulationduring angular and radial shaft misalignment.

FIG. 6 is a sectional view of a second embodiment of the shaft sealassembly as shown in FIG. 2.

FIG. 7 is a sectional view of a third embodiment as shown in FIG. 2.

FIG. 8 is a perspective view of a fourth embodiment as mounted to avessel wall.

FIG. 9 is a cross-sectional view of a first embodiment of the pressurebalanced shaft seal assembly mounted to a housing wherein the shaft isin alignment.

FIG. 9A is a detailed view of the portion of the first embodiment of thepressure balanced shaft seal assembly adjacent the vent wherein theshaft is in alignment.

FIG. 9B is a detailed view of the portion of first embodiment of thepressure balanced shaft seal assembly adjacent the fluid return pathwaywherein the shaft is in alignment.

FIG. 10 is a cross-sectional view of the first embodiment of thepressure balanced shaft seal assembly shown during shaft misalignment.

FIG. 10A is a detailed view of the portion of the first embodiment ofthe pressure balanced shaft seal assembly adjacent the vent wherein theshaft is misaligned.

FIG. 10B is a detailed view of the portion of the first embodiment ofthe pressure balanced shaft seal assembly adjacent the fluid returnpathway wherein the shaft is misaligned.

FIG. 11 is a cross-sectional view of a second embodiment of the pressurebalanced shaft seal assembly wherein the shaft is in alignment.

FIG. 12 is a cross-sectional view of a third embodiment of the pressurebalanced shaft seal assembly wherein the shaft is in alignment.

DETAILED DESCRIPTION Element Listing

Description Element No. Shaft  1 Fixed stator  2 Fixed stator(part-line)  2a Labyrinth seal  3 Radiused face  3a Floating stator  4Fluid return pathway  5 Shaft seal clearance  6 First o-ring  7Anti-rotation pin  8 Vent  9 Anti-rotation groove (floating stator) 10Spherical interface 11 Anti-rotation pin 12 Second o-ring 13 Labyrinthseal pattern grooves 14 First o-ring channel 15 Cavity for anti-rotationdevice (fixed stator) 16 Axial face of labyrinth seal 17 Axial face offloating stator 18 Second o-ring channel 19 First clearance betweenfloating stator/fixed stator 20 Second clearance between floatingstator/fixed stator 21 Throttle groove 22 Labyrinth pattern annulargroove 23 Sleeve 24 Shaft seal assembly 25 Throttle (alignment skate) 26Floating stator annular groove 27 Labyrinth seal passage 28 Floatingstator passage 29 Housing 30 Angle of misalignment 31 Bearings andbearing cavity 32 Mounting bolts 33 Vessel wall 34 Pressure balancedshaft seal assembly 40 Labyrinth seal interior face 42 Floating statorinterior face 44 Pressure balancing annular channel 46 First radialinterface  47a Second radial interface  47b Fixed stator annular groove48 Annular groove radial-interior surface  48a

DETAILED DESCRIPTION

Before the various embodiments of the present invention are explained indetail, it is to be understood that the invention is not limited in itsapplication to the details of construction and the arrangements ofcomponents set forth in the following description or illustrated in thedrawings. The invention is capable of other embodiments and of beingpracticed or of being carried out in various ways. Also, it is to beunderstood that phraseology and terminology used herein with referenceto device or element orientation (such as, for example, terms like“front”, back “up”, “down”, “top”, “bottom”, and the like) are only usedto simplify description of the present invention, and do not aloneindicate or imply that the device or element referred to must have aparticular orientation. In addition, terms such as “first”, “second”,and “third” are used herein and in the appended claims for purposes ofdescription and are not intended to indicate or imply relativeimportance or significance. Furthermore, any dimensions recited orcalled out herein are for exemplary purposes only and are not meant tolimit the scope of the invention in any way unless so recited in theclaims.

FIGS. 1-5 provide a view of a first embodiment of the shaft sealassembly 25 that allows for sealing various lubricating solutions withinbearing housing 30. FIGS. 6 and 7 provide alternative embodiments of theshaft seal assembly 25 wherein sealing fluids are used. Applicant hereindefines sealing fluids to include both liquids and vapors. Applicantconsiders air, nitrogen, water and steam as well as any other fluidwhich may work with the proposed shaft seal assembly to provide apressurized fluid barrier for any and all embodiments disclosed hereinto be within the purview of the present disclosure. The gas or fluidchosen is based on process suitability with the product to be sealed.

FIG. 1 is a perspective exterior view of the shaft seal assembly 25arranged and engaged with a shaft 1 inserted through the fixed stator 2of shaft seal assembly 25. FIG. 2 is an exterior end view of the shaftseal assembly with shaft 1 aligned within the shaft seal assembly 25.

FIG. 3 is a sectional view of a first embodiment of the shaft sealassembly 25 shown in FIG. 2 illustrating the shaft seal assembly 25 as alabyrinth seal for retaining lubrication solution within the bearingcavity 32 of housing 30. The shaft 1 shown in FIG. 3 is the type whichmay experience radial, angular or axial movement relative to the fixedstator element or portion of the fixed stator 2 during rotation. Thefixed stator portion of the shaft seal assembly 25 may be flange-mountedor press-fit or attached by other means to a housing 30. The inventionwill also function with a rotating housing and stationary shaft. (Notshown) As required by the particular application, the shaft 1 is allowedto move freely in the axial direction in relation to the shaft sealassembly 25.

A labyrinth seal 3 having an interior surface is engaged with shaft 1. Adefined clearance 6 exists between the interior surface of saidlabyrinth seal 3 and the shaft 1. Opposite the interior surface of saidlabyrinth seal 3 is the radiused surface 3 a of said labyrinth seal 3.The radiused surface 3 a of the labyrinth seal 3 and the interior of thefloating stator 4 forms a spherical interface 11. O-ring channels 15 andO-rings 7 are disposed to cooperate with said radiused surface 3 a ofsaid labyrinth seal 3 to seal (or trap) fluid migration through, betweenand along engaged labyrinth seal 3 and floating stator 4 whilemaintaining spherical interface 11 which allows limited relativerotational movement (articulation) between labyrinth seal 3 and floatingstator 4. O-ring channels 15, as shown, are machined into the floatingstator 4 and positioned at the spherical interface 11 with labyrinthseal 3. O-ring channels 15 are annular and continuous in relation tolabyrinth seal 3. The o-ring channel 15 and o-ring 7 may also be placedin the labyrinth seal 3 adjacent the spherical interface 11. O-rings 7should be made of materials that are compatible with both the product tobe sealed and the preferred sealing fluid chosen. O-ring channels 15 ando-rings 7 are one possible combination of sealing means that may be usedwithin the shaft seal assembly 25 as recited in the claims.Strategically placed anti-rotation pin(s) 12 inserted into anti-rotationgrooves 10 limit relative rotational movement between labyrinth seal 3and floating stator 4. A plurality of anti-rotation grooves 10 and pins12 may be placed around the radius of the shaft 1. If the shaft sealassembly 25 is used in combination with a sealing fluid, strategicanti-rotation pins 12 may be removed allowing correspondinganti-rotation grooves 10 to serve as a fluid passage through vent 9 andlubricant return 5. (See FIG. 7) Additionally, the relationship of thediameters of anti-rotation pins 12 and anti-rotation grooves 10 may beselected to allow more or less angular misalignment of the shaft 1. Asmall diameter anti-rotation pin 12 used with a large diameteranti-rotation groove 10 would allow for greater relative movement of thelabyrinth seal 3 in relation to the floating stator 4 in response toangular misalignment of shaft 1. Labyrinth seal 3 is one possibleembodiment of a sealing means that may be used adjacent to the shaft 1within the shaft seal assembly 25 as recited in the claims.

A continuous annular channel is formed within fixed stator 2 and definedby clearance 20 and 21 as allowed between the exterior of said floatingstator 4 and said interior of said fixed stator 2 of shaft seal assembly25. The annular channel of fixed stator 2 is highlighted as A-A′ in FIG.2. The annular channel of the fixed stator has interior surfaces whichare substantially perpendicular to said shaft 1. The exterior surfacesof the floating stator 4, which is substantially encompassed within theannular channel of the fixed stator 2, cooperatively engage with thefirst and second interior perpendicular faces of the fixed stator 2. Aninner annular interface is formed by the first (shaft seal assemblyinboard side) perpendicular annular channel surface of the fixed stator2 engaging with the first (inboard side) perpendicular face of thefloating stator 4. An outer annular interface is formed by the second(shaft seal assembly outboard side) perpendicular annular interiorchannel surface of the fixed stator 2 engaging with the second (outboardside) perpendicular face of the floating stator 4. O-ring channels 19and o-rings 13 disposed therein cooperate with the surfaces of floatingstator 4 which are in perpendicular to relation to shaft 1 to seal (ortrap) fluid migration between and along engaged floating stator 4 whileallowing limited relative rotational movement between floating stator 4and fixed stator 2. Floating stator 4 and fixed stator 2 are onepossible embodiment of cooperatively engaged sealing means that may beused in combination with labyrinth seal 3 within the shaft seal assembly25 as recited in the claims.

O-ring channels 19 are annular and continuous in relation to shaft 1.The o-ring channels 19 and o-rings 13 may be placed in the body of thefloating stator 4 instead of the fixed stator 2 (not shown) but must beplaced in similar proximal relation. O-rings 13 should be made ofmaterials that are compatible with both the product to be sealed and thepreferred sealing fluid chosen. O-ring channels 19 and o-rings 13 areone possible combination of sealing means that may be used within theshaft seal assembly 25 as recited in the claims.

Strategically placed anti-rotation pin(s) 8 inserted into anti-rotationgroove(s) 16 limit both relative radial and rotational movement betweenfloating stator 4 and interior side of fixed stator 2. A plurality ofanti-rotation grooves 16 and pins 8 may be placed around the radius ofthe shaft 1. The relationship of the diameters of anti-rotation pins 8and anti-rotation grooves 16 may also be selected to allow more or lessangular misalignment of the shaft. A small diameter anti-rotation pin 8and large diameter fixed stator anti-rotation groove allow for greaterrelative movement of the labyrinth seal 3 in response to angularmisalignment of shaft 1.

The labyrinth pattern seal grooves 14 may be pressure equalized byventing through one or more vents 9. If so desired, the vents may besupplied with a pressurized sealing fluid to over-pressurize thelabyrinth area 14 and shaft seal clearance 6 to increase the efficacy ofshaft seal assembly 25. A spherical interface 11 between the labyrinthseal 3 and the floating stator 4 allow for angular misalignment betweenthe shaft 1 and fixed stator 2. O-ring channels 19 are annular with theshaft 1 and, as shown, are machined into the fixed stator 2 andpositioned at the interface between the fixed stator 2 and floatingstator 4. O-ring channel 19 may also be placed in the floating stator 4for sealing contact with the fixed stator 2.

FIG. 3A illustrates seal-shaft integrity during angular and radial shaftalignment. This view highlights the alignment of the axial face 17 ofthe labyrinth seal 3 and the axial face 18 of the floating stator 4.Particular focus is drawn to the alignment of the axial faces 17 and 18at the spherical interface 11 between the floating stator 4 andlabyrinth 3. FIG. 3B illustrates the shaft-seal integrity during angularand radial shaft alignment at the surface opposite that shown in FIG.3A. This view highlights the alignment of the axial faces 17 and 18 oflabyrinth seal 3 and floating stator 4, respectively, for the oppositeportion of the shaft seal assembly 25 as shown in FIG. 3A. Thosepracticed in the arts will appreciate that because the shaft 1 and shaftseal assembly 25 are of a circular shape and nature, the surfaces areshown 360 degrees around shaft 1. Again, particular focus is drawn tothe alignment of the axial faces 17 and 18 at the spherical interface 11between the labyrinth seal 3 and floating stator 4. FIGS. 3A and 3B alsoillustrate the first defined clearance 20 between the floating stator 4and the fixed stator 2 and the second defined clearance 21 between thefloating stator 4 and fixed stator 2 and opposite the first definedclearance 20.

In FIGS. 2, 3, 3A and 3B, the shaft 1 is not experiencing radial,angular or axial movement and the width of the defined clearances 20 and21, which are substantially equal, indicate little movement ormisalignment upon the floating stator 4.

FIG. 4 is an exterior end view of the shaft seal assembly 25 with therotatable shaft 1 misaligned therein. FIG. 5 is a sectional view of thefirst embodiment of the shaft seal assembly 25 as shown in FIG. 3 withboth angular and radial misalignment of the shaft 1 applied. The shaft 1as shown in FIG. 5 is also of the type which may experience radial,angular or axial movement relative to the fixed stator 2 portion of theshaft seal assembly 25.

As shown at FIG. 5, the defined radial clearance 6 of labyrinth seal 3with shaft 1 has been maintained even though the angle of shaftmisalignment 31 has changed. The shaft 1 is still allowed to move freelyin the axial direction even though the angle of shaft misalignment 31has changed. The arrangement of the shaft seal assembly 25 allows thelabyrinth seal 3 to move with the floating stator 4 upon introduction ofradial movement of said shaft 1. The labyrinth seal 3 and floatingstator 4 are secured together by one or more compressed o-rings 7.Rotation of the labyrinth seal 3 within the floating stator 4 isprevented by anti-rotation means which may include a screws, pins orsimilar devices 12 to inhibit rotation. Rotation of the labyrinth seal 3and floating stator 4 assembly within the fixed stator 2 is prevented byanti-rotation pins 8. The pins as shown in FIGS. 3, 3A, 3B, 5, 6 and 7are one means of preventing rotation of the labyrinth seal 3 andfloating stator 4, as recited in the claims. Lubricant or other media tobe sealed by the labyrinth seal 3 may be collected and drained through aseries of one or more optional drains or lubricant return pathways 5.The labyrinth seal 3 may be pressure equalized by venting through one ormore vents 9. If so desired, the vents 9 may be supplied withpressurized air or other gas or fluid media to over-pressurize thelabyrinth seal 3 to increase seal efficacy. The combination of closetolerances between the cooperatively engaged mechanical portions of theshaft seal assembly 25 and pressurized sealing fluid inhibit product andcontaminate contact with the internals of the shaft seal assembly 25.The spherical interface 11 between the labyrinth seal 3 and the floatingstator 4 allow for angular misalignment between the shaft 1 and fixedstator 2. O-ring channel 19 and o-ring 13 disposed therein cooperatewith the opposing faces of the floating stator 4, which aresubstantially in perpendicular relation to shaft 1, to seal (or trap)fluid migration between and along engaged floating stator 4 whileallowing limited relative radial (vertical) movement between stator 4and fixed stator 2.

FIG. 5A illustrates seal-shaft integrity allowed by the shaft sealassembly 25 during angular and radial shaft misalignment. This viewhighlights the offset or articulation of the axial faces 17 of thelabyrinth seal in relation the axial faces 18 of the floating stator 4for a first portion of the shaft seal assembly 25. Particular focus isdrawn to the offset of the axial faces 17 and 18 at the sphericalinterface 11 between labyrinth seal 3 and floating stator 4.

FIG. 5B illustrates seal-shaft integrity for a second surface, oppositethe first surface shown in FIG. 5A, during angular and radial shaftmisalignment. This view highlights that during misalignment of shaft 1,axial faces 17 and 18, of the labyrinth seal 3 and floating stator 4,respectively, are not aligned but instead move (articulate) in relationto each other. The shaft to seal clearance 6 is maintained in responseto the shaft misalignment and the overall seal integrity is notcompromised because the seal integrity of the floating stator 4 to fixedstator 2 and the floating stator 4 to labyrinth seal 3 are maintainedduring shaft misalignment. Those practiced in the arts will appreciatethat because the shaft 1 and shaft seal assembly 25 are of a circularshape and nature, the surfaces are shown 360 degrees around shaft 1.

FIGS. 5A and 5B also illustrate the first clearance or gap 20 betweenthe floating stator 4 and the fixed stator 2 and the second clearance orgap 21 between the floating stator 4 and fixed stator 2 and opposite thefirst clearance or gap 20.

In FIGS. 4, 5, 5A and 5B, the shaft 1 is experiencing radial, angular oraxial movement during rotation of the shaft 1 and the width of the gapsor clearances 20 and 21, have changed in response to said radial,angular or axial movement. (Compare to FIGS. 3, 3A and 3B.) The changein width of clearance 20 and 21 indicate the floating stator 4 has movedin response to the movement or angular misalignment of shaft 1. Theshaft seal assembly 25 allows articulation between axial faces 17 and18, maintenance of spherical interface 11 and radial movement at firstand second clearance, 20 and 21, respectively, while maintaining shaftseal clearance 6.

FIG. 6 is a sectional view of a second embodiment of the shaft sealassembly 25 as shown in FIG. 2 for over-pressurization with alternativelabyrinth seal pattern grooves 14. In this figure the labyrinth sealpattern grooves 14 are composed of a friction reducing substance such aspolytetrafluoroethylene (PTFE) that forms a close clearance to the shaft1. PTFE is also sometimes referred to as Teflon® which is manufacturedand marketed by Dupont. PTFE is a plastic with high chemical resistance,low and high temperature capability, resistance to weathering, lowfriction, electrical and thermal insulation, and “slipperiness.” The“slipperiness” of the material may also be defined as lubricous oradding a lubricous type quality to the material. Carbon or othermaterials may be substituted for PTFE to provide the necessary sealingqualities and lubricous qualities for labyrinth seal pattern grooves 14.

Pressurized sealing fluids are supplied to over-pressurize thelubricious labyrinth pattern 26 as shown in FIG. 6. The pressurizedsealing fluids make their way into the annular groove 23 of the throttle26 through one or more inlets. Throttle 26 is also referred to as “analignment skate” by those practiced in the arts. Throttle 26 allows thelabyrinth seal 3 to respond to movement of the shaft caused by themisalignment of the shaft 1. The pressurized sealing fluid escapes pastthe close clearance formed between the shaft 1 and labyrinth seal 3having throttle 26. The close proximity of the throttle 26 to the shaft1 also creates resistance to the sealing fluid flow over the shaft 1 andcauses pressure to build-up inside the annular groove 23. Floatingannular groove 27 in cooperation and connection with annular groove 23also provides an outlet for excess sealing fluid to be “bled” out ofshaft seal assembly 25 for pressure equalization or to maintain acontinuous fluid purge on the shaft sealing assembly 25 duringoperation. An advantage afforded by this aspect of the shaft sealingassembly 25 is its application wherein “clean-in place” product sealdecontamination procedures are preferred or required. Examples wouldinclude food grade applications.

FIG. 7 illustrates shaft seal assembly 25 with the anti-rotation pin 12removed to improve visualization of the inlets. These would typicallyexist, but are not limited to, a series of ports, inlets or passagesabout the circumference of the shaft seal assembly 25. FIG. 7 also showsthe shape and pattern of the labyrinth seal 3 may be varied. The shapeof throttles 26 may also be varied as shown by the square profile shownat throttle groove 22 in addition to the circular-type 26. Also notethat where direct contact with the shaft 1 is not desired, the shaftseal assembly 25 be used in combination with a separate sleeve 24 thatwould be attached by varied means to the shaft 1.

FIG. 8 shows that another embodiment of the present disclosure whereinthe shaft seal assembly 25 has been affixed to a vessel wall 34. Theshaft seal assembly 25 may be affixed to vessel wall 34 throughsecurement means such as mounting bolts 33 to ensure improved sealingwherein shaft 1 is subjected to angular misalignment. The mounting bolts33 and slots (not numbered) through the shaft seal assembly 25 exteriorare one means of mounting the shaft seal assembly 25, as recited in theclaims.

In certain applications, especially those wherein the process side ofshaft seal assembly 25 (generally the area to the left of the shaft sealassembly 25 as shown in FIGS. 3-3B and 5-7) is at an increased pressure,it is desirable for the shaft seal assembly 25 to be configured tobalance the pressure experienced by the shaft seal assembly 25 in theaxial direction. A pressure balanced shaft seal assembly 40 thatbalances the pressure (in the axial direction) the product applies tothe labyrinth seal interior face 42 and floating stator interior face 44is shown in FIGS. 9-12.

In the first embodiment of the pressure balanced shaft seal assembly asshown in FIGS. 9-10B, the shaft sealing member (i.e., the labyrinth seal3 in combination with the floating stator 4) includes a pressurebalancing annular channel 46. Save for the pressure balancing annularchannel 46, the pressure balanced shaft seal assembly 40 operates in thesame manner as the shaft seal assembly 25 shown in FIGS. 1-8 anddescribed in detail above. That is, the floating stator 4 is positionedin the fixed stator annular groove 48. The first clearance betweenfloating stator/fixed stator 20, which in the embodiments picturedherein is between the floating stator radial-exterior surface 45 and theannular groove radial-interior surface 48 a (shown in FIGS. 9A and 9B),accounts at least for radial perturbations of the shaft 1. The sphericalinterface 11 between the floating stator 4 and the labyrinth seal 3accounts at least for angular perturbations of the shaft 1.

The pressure balancing annular channel 46 is formed in the floatingstator 4 adjacent the first radial interface 47 a between the floatingstator 4 and the fixed stator 2, as shown in FIGS. 9-10 for the firstembodiment. As shown in the various embodiments pictured herein, thefirst radial interface 47 a between the floating stator 4 and the fixedstator 2 is adjacent the portion of the fixed stator 2 fashioned withthe cavity for anti-rotation device 16. That is, the axial face of thefloating stator 4 that is positioned within the fixed stator 2 andfurthest from the process side of the pressure balanced shaft sealassembly 40. A second radial interface 47 b between the floating stator4 and fixed stator 2, which is substantially parallel to the firstradial interface 47 a, is positioned closer to the process side of thepressure balanced shaft seal assembly 40 as compared to the first radialinterface 47 a.

In many applications the optimal radial dimension of the pressurebalancing annular channel 46 will be the substantially similar to theradial dimension of the floating stator interior face 44 so that thearea of the floating stator 4 acted upon by the product and the area ofthe floating stator 4 acted upon by the sealing fluid have equal surfaceareas. In such a configuration, the axial forces will balance if theproduct and the sealing fluid are pressurized to approximately the samevalue. Accordingly, the optimal radial dimension of the pressurebalancing annular channel 46 will depend on the design characteristicsof the entire system, and the radial dimension of the pressure balancingannular channel 46 may be any suitable amount for a particularapplication, whether greater or less than the radial dimension of thefloating stator interior face 44. The axial dimension of the pressurebalancing annular channel 46 will also vary depending on the designcharacteristics of the entire system, including but not limited to thespecific sealing fluid that is used, the product pressure, and thepressure of the sealing fluid. In some applications the optimal axialdimension of the pressure balancing annular channel 46 will be 0.005 ofan inch, but may be greater in other embodiments and less in still otherembodiments.

The pressure balancing annular channel 46 allows sealing fluidintroduced into the first clearance between floating stator/fixed stator20 (from where the sealing fluid may enter the pressure balancingannular channel 46) to act upon the floating stator in an axialdirection. Typically, the process side of the pressure balanced shaftseal assembly 40 (generally the area to the left of the pressurebalanced shaft seal assembly 40 as shown in FIGS. 9-12) experiencesforces from the process fluid acting upon the labyrinth seal interiorface 42 and floating stator interior face 44. These forces are mostoften due to the pressure generated by the rotating equipment to whichthe shaft 1 is coupled. For example, if the shaft 1 is coupled to afluid pump generating seventy pounds per square inch (psi) of headpressure, the process side of the pressure balanced shaft seal assembly40 will be pressurized to approximately seventy psi. This pressurizedfluid will act upon the labyrinth seal interior face 42 and floatingstator interior face 44, and consequently urge the labyrinth seal 3 andfloating stator 4 in the axial direction away from the process side ofthe pressure balancing shaft seal assembly 40 (i.e., generally to theright side of the drawing as depicted in FIGS. 9-12). By contrast,sealing fluid located in the pressure balancing annular channel 46 willurge the labyrinth seal 3 and floating stator 4 in the axial directiontoward the process side of the pressure balancing shaft seal assembly40, which may substantially cancel the axial force the product exertsupon the pressure balancing shaft seal assembly 40, depending on thedesign of the sealing fluid system.

FIGS. 11 and 12 show a second and third embodiment of the pressurebalanced shaft seal assembly 40. The second and third embodiments of thepressure balanced shaft seal assembly 40 generally correspond to thesecond and third embodiments of the shaft seal assembly 25 as shown inFIGS. 7 and 8 and described in detail above. However, as with the firstembodiment of the pressure balanced shaft seal assembly 40 as shown inFIGS. 9-10B, the second and third embodiments include a pressurebalancing annular channel 46.

The various embodiments of the pressure balanced shaft seal assembly 40pictured and described herein are formed with a fixed stator 2 andfloating stator 4 that are comprised of two distinct portions. Theseembodiments facilitate assembly of the pressure balanced shaft sealassembly 40 since in the embodiments pictured herein the majority of thefloating stator 4 is positioned within the fixed stator 2. Wheninstalling a pressure balanced shaft seal assembly 40 according to thefirst embodiment (as pictured in FIGS. 9-10B), the first portion offixed stator 2 (i.e., the portion adjacent the process side of thepressure balanced shaft seal assembly 40) would be affixed to a housing30. Next, the floating stator 4 and labyrinth seal 3 may be positionedas one assembled piece (wherein the components forming the sphericalinterface 11 have been preassembled) between the shaft 1 and the firstportion of the fixed stator 2. The placement of the floating stator 4and labyrinth seal 3 within the fixed stator 3 forms the second axialinterface 47 b between the fixed stator 2 and floating stator 4.Finally, the second portion of the fixed stator 2 (i.e., the portionfurthest from the process side of the pressure balanced shaft sealassembly 40) may be positioned adjacent to and affixed to the firstportion of the fixed stator 2. The positioning of the second portion ofthe fixed stator 2 subsequently forms the first radial interface 47 abetween the fixed stator 2 and floating stator 4.

Alternatively, the floating stator 4 and labyrinth seal 3 may beseparately positioned within the fixed stator annular groove 48. Forexample, after the first portion of the fixed stator 2 has been affixedto the housing 30, the first portion of the floating stator 4 may bepositioned within the fixed stator annular groove 48. The placement ofthe first portion of the floating stator 4 within the fixed statorannular groove 48 forms the second axial interface 47 b between thefixed stator 2 and floating stator 4. Next, the labyrinth seal 3 may bepositioned adjacent the shaft 3, the placement of which forms a portionof the spherical interface 11 between the floating stator 4 andlabyrinth seal 3. Next, the second portion of the floating stator 4 maybe positioned adjacent the first portion of the floating stator 4 andaffixed thereto with a plurality of anti-rotation pins 8, whichcompletes the spherical interface 11 between the floating stator 4 andlabyrinth seal 3. Finally, the second portion of the fixed stator 2 isaffixed to the first portion of the fixed stator 2 with a plurality ofbolts or rivets, the placement of which forms the first axial interface47 a between the floating stator 4 and fixed stator 2. Any suitablesecuring members known to those skilled in the art may be used to affixthe first and second portions of the floating stator 4 to one another orto affix the first and second portions of the fixed stator 2 to oneanother.

Although the embodiments pictured herein are directed to pressurebalanced shaft seal assemblies 40 wherein the fixed stator 2 andfloating stator 4 are comprised of two separate portions, in otherembodiments not pictured herein, the fixed stator 2 and/or floatingstator 4 are formed of one integral member.

Having described the preferred embodiment, other features of the presentinvention will undoubtedly occur to those versed in the art, as willnumerous modifications and alterations in the embodiments of theinvention illustrated, all of which may be achieved without departingfrom the spirit and scope of the present disclosure.

1. A shaft seal assembly comprising: a. a fixed stator, wherein saidfixed stator is secured within a housing, and wherein said fixed statoris formed with an annular groove along a portion of the radial-interiorsurface thereof; b. a shaft sealing member, wherein said shaft sealingmember fits within said annular groove of said fixed stator, and whereinsaid shaft sealing member comprises: i. a floating stator, wherein theradial-exterior surface of said floating stator is separated from saidannular groove radial-interior surface in the radial dimension by apredetermined amount to create a first clearance between said floatingstator and said fixed stator, wherein the radial-interior surface ofsaid floating stator is substantially concave in shape, and wherein saidfloating stator having an annular recess and said fixed stator having asurface corresponding to said annular recess to form a pressurebalancing annular channel therein; and, ii. a labyrinth seal, whereinsaid labyrinth seal has a radial-exterior surface with a substantiallyconvex shape that corresponds to the radial-interior surface of saidfloating stator so as to create a spherical interface therebetween,wherein said labyrinth seal has a radial-interior surface with aplurality of labyrinth pattern annular grooves, and wherein saidlabyrinth seal radial-interior surface is positioned adjacent arotatable shaft.
 2. The shaft seal assembly according to claim 1 whereinthe radial-exterior surface of said floating stator is non-linear. 3.The shaft seal assembly according to claim 1 wherein said floatingstator is axially located through first and second radial interfacesbetween said floating stator and said annular groove of said fixedstator.
 4. The shaft seal assembly according to claim 3 furthercomprising first and second O-ring channels fashioned in said fixedstator at said first and second radial interfaces, respectively, whereinone O-ring is positioned in each said first and second O-ring channel.5. The shaft seal assembly according to claim 1 wherein a plurality ofradially oriented anti-rotation grooves are fashioned in said labyrinthseal, and wherein a plurality of corresponding anti-rotation pins arepositioned within said anti-rotation grooves and within a portion ofsaid floating stator adjacent said anti-rotation grooves in saidlabyrinth seal.
 6. The shaft seal assembly according to claim 1 whereina plurality of axially oriented anti-rotation grooves are fashioned insaid fixed stator, and wherein a plurality of correspondinganti-rotation pins are positioned within said anti-rotation grooves andwithin a portion of said floating stator adjacent said anti-rotationgrooves in said fixed stator.
 7. The shaft seal assembly according toclaim 1 further comprising a plurality of O-ring channels fashioned inthe radial-interior surface of said floating stator, wherein one O-ringis positioned in each said O-ring channel.
 8. The shaft seal assemblyaccording to claim 1 further comprising a first fluid return pathwayfashioned in said labyrinth seal, a second fluid return pathwayfashioned in said floating stator, and a third fluid return pathwayfashioned in said fixed stator, wherein said first, second, and thirdfluid return pathways are in fluid communication with one another. 9.The shaft seal assembly according to claim 1 wherein said floatingstator is further defined as being constructed of two distinct portionsaffixed to one another.
 10. The shaft seal assembly according to claim 1wherein said fixed stator is further defined as being constructed of twodistinct portions affixed to one another.
 11. The shaft seal assemblyaccording to claim 1 further comprising a vent formed in said fixedstator, wherein said vent fluidly connects the exterior of said fixedstator with said annular groove formed in said fixed stator.
 12. Theshaft seal assembly according to claim 1 wherein said fixed stator isfurther defined as being secured to a housing via a portion of theradial-exterior surface of said fixed stator and a correspondingradial-interior surface of an aperture formed in said housing.
 13. Theshaft seal assembly according to claim 1 wherein said fixed stator isfurther defined as being secured to a housing via a plurality ofmounting bolts passing through a corresponding plurality of apertures insaid fixed stator and terminating in a corresponding plurality of boltholes in said housing.
 14. The shaft seal assembly according to claim 1further comprising: a. an annular seal fluid groove fashioned in theradial-interior surface of said labyrinth seal; b. a seal fluid inletfashioned in the radial-exterior surface of said fixed stator; c. afirst passage fashioned in said floating stator, wherein said firstpassage is in fluid communication with said seal fluid inlet; d. a firstpassage fashioned in said labyrinth seal, wherein said first passage insaid labyrinth seal is in fluid communication with said first passage insaid floating stator and said annular seal fluid groove; e. a seal fluidoutlet fashioned in the radial-exterior surface of said fixed stator; f.a second passage fashioned in said floating stator, wherein said secondpassage is in fluid communication with said seal fluid outlet; and g. asecond passage fashioned in said labyrinth seal, wherein said secondpassage in said labyrinth seal is in fluid communication with saidsecond passage in said floating stator and said annular seal fluidgroove.
 15. The shaft seal assembly according to claim 14 furthercomprising an alignment skate positioned in each said annular groove ofsaid plurality of labyrinth pattern annular grooves.
 16. The shaft sealassembly according to claim 15 wherein said alignment skates are furtherdefined as having the required dimension to contact said rotatableshaft.
 17. The shaft seal assembly according to claim 16 wherein saidshaft seal assembly is further defined as including a pressurized sealfluid introduced into said shaft seal assembly through said seal fluidinlet.
 18. The shaft seal assembly according to claim 17 wherein saidpressurized seal fluid is further defined as a gas.
 19. The shaft sealassembly according to claim 17 wherein said pressurized seal fluid isfurther defined as a liquid.
 20. The shaft seal assembly according toclaim 18 wherein said shaft seal assembly is further defined so that theclearance between said plurality of labyrinth pattern annular grooves insaid labyrinth seal and said rotatable shaft is such that apredetermined amount of said pressurized seal fluid may pass betweensaid plurality of labyrinth pattern annular grooves and said rotatableshaft.
 21. The shaft seal assembly according to claim 19 wherein saidshaft seal assembly is further defined so that the clearance betweensaid plurality of labyrinth pattern annular grooves in said labyrinthseal and said rotatable shaft is such that a predetermined amount ofsaid pressurized seal fluid may pass between said plurality of labyrinthpattern annular grooves and said rotatable shaft.
 22. The shaft sealassembly according to claim 19 wherein said seal fluid outlet is furtherdefined as including a purge stream for said pressurized sealing fluid.